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Comparison of Antero-Lateral Versus Antero-Posterior ElectrodePosition for Biphasic External Cardioversion of Atrial Flutter†

Tim Risius, MD*, Kai Mortensen, MD, Tjark F. Schwemer, MD, Muhammet A. Aydin, MD,Hanno U. Klemm, MD, Rodolfo Ventura, MD, Achim Barmeyer, MD, Boris Hoffmann, MD,

Thomas Rostock, MD, Thomas Meinertz, MD, and Stephan Willems, MD

External cardioversion is an established and very important tool to terminate symptomaticatrial flutter. The superiority of the biphasic waveform has been demonstrated for atrialflutter, but whether electrode position affects the efficacy of cardioversion in this popula-tion is not known. The aim of this trial was to evaluate whether anterior-lateral (A-L)compared with anterior-posterior (A-P) electrode position improves cardioversion results.Of 130 screened patients, 96 (72 men, mean age 62 � 12 years) were included and randomlyassigned to a cardioversion protocol with either A-L or A-P electrode position. In eachgroup, 48 patients received sequential biphasic waveform shocks using a step-up protocolconsisting of 50, 75, 100, 150, or 200 J. The mean energy (65 � 13 J for A-L vs 77 � 13 Jfor A-P, p � 0.001) and mean number of shocks (1.48 � 1.01 for A-L vs 1.96 � 1.00 for A-P,p � 0.001) required for successful cardioversion were significantly lower in the A-L group.The efficacy of the first shock with 50 J in the A-L electrode position (35 of 48 patients[73%]) was also highly significantly greater than the first shock with 50 J in the A-Pelectrode position (18 of 48 patients [36%]) (p � 0.001). In conclusion, the A-L electrodeposition increases efficacy and requires fewer energy and shocks in external electricalcardioversion of common atrial flutter. Therefore, A-L electrode positioning should berecommended for the external cardioversion of common atrial flutter. © 2009 Elsevier

Inc. All rights reserved. (Am J Cardiol 2009;104:1547–1550)

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Common atrial flutter is a highly prevalent atrial arrhyth-ia1,2 caused by trapped excitation in the right atrium.3,4

hromboembolic stroke5–7 and uncontrolled ventricular rateue to loss of atrial function are common complications andause morbidity and mortality in affected patients.1,8 Thereatment for atrial flutter is the restoration of sinus rhythm,hich can be achieved by the administration of antiarrhyth-ic drugs,9 overdrive stimulation, catheter ablation, and

ransthoracic electrical cardioversion.10 For a defined pa-ient population (e.g., acute symptomatic patients), externallectrical cardioversion is a substantial first-line treatmenthat is commonly available. Cardioversion techniques andevices for different rhythm disorders are clinically inves-igated.11–13 Among these, the allocation of the electrodes ishe focus of interest. Different electrode positions have beenroposed; the anterior-posterior (A-P) and anterior-lateralA-L) electrode positions are the most recommended andsed variants.13–16 Trials of the electrical cardioversion oftrial fibrillation have shown that the A-P position hasreater efficacy than the A-L position.15,16 For commontrial flutter, the optimal position for placing the electrodess yet unknown. This prospective trial was designed to

University Hospital Hamburg-Eppendorf, Heart Center, Department ofardiology, Hamburg, Germany. Manuscript received March 23, 2009;

evised manuscript received and accepted July 2, 2009.*Corresponding author: Tel: 49-40-74105-4120; fax: 49-40-74105-2967.E-mail address: risius@uke.uni-hamburg.de (T. Risius).

† This study was presented in part at the 28th Annual Scientific Session

pf the Heart Rhythm Society, Denver, Colorado, May 9 to 12, 2007.

002-9149/09/$ – see front matter © 2009 Elsevier Inc. All rights reserved.oi:10.1016/j.amjcard.2009.07.027

etermine the efficacy of the different electrode positions ingroup of patients with symptomatic atrial flutter with

ndications for acute electrical cardioversion.

ethods

This was a prospective, randomized, single-center trial toompare the efficacy of the A-P electrode position to that ofhe A-L electrode position in the electrical cardioversion ofommon atrial flutter. We screened 130 patients in ourutpatient clinic, emergency room, intensive care unit, orards. Patients were eligible for the study if, according to

urrent guidelines, the electrical cardioversion of atrial flut-er was indicated by, for example, imminent cardiac decom-ensation, hypotension, or angina pectoris. Patients wereneligible for this trial if they aged �18 years, pregnant, orlanned for cardioversion of arrhythmias other than com-on atrial flutter. All patients underwent diagnostic proce-

ures and eventual treatment for the prevention of embolictroke and systemic embolism according to actual guide-ines14 for the management of patients with atrial fibrillationr flutter. After cardioversion, all patients were required toe anticoagulated for �4 weeks.14 The local ethics com-ittee approved the study, and the study was in complianceith the Declaration of Helsinki. All patients gave written

nformed consent. The study was registered at ClinicalTrials.ov (protocol record UKE-2383). The hypothesis was that 1f 2 (A-L vs A-P) electrode positions would have greaterfficacy than the other for the cardioversion of atrial flutter.he efficacy of the 2 different electrode positions was the

rimary end point. As secondary end points, we defined the

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1548 The American Journal of Cardiology (www.AJConline.org)

ean energy requirement, the mean number of cardiover-ion shocks, and cumulative cardioversion efficacy. Directlyefore cardioversion, patients were randomized in a 1:1atio to undergo cardioversion in either the A-P or A-Llectrode position by computer-generated randomization.or all cardioversion procedures, a Zoll M-Series devicend Zoll MFE self-adhesive pads (Zoll Medical, Chelms-ord, Massachusetts) were used. Patients were sedated withropofol and/or midazolam at the physician’s discretion.ardioversion was done under general anesthesia in theostabsorptive state. Successful cardioversion was defineds conversion from atrial flutter to sinus rhythm for �30econds.

The shock protocol and starting energies were based onhe findings of Kerber et al16 and Kerber.17 Patients receivedequential shocks of increasing energy of 50, 75, 100, 150,r 200 J as necessary for successful cardioversion. A cross-ver between electrode positions was planned in case of autile shock of 200 J for a final second shock of 200 J with

able 1atient characteristics

ariable All A-P A-L pValue(n � 96) (n � 48) (n � 48)

ge (years) 62 � 12 62 � 12 62 � 13 0.14en 72 (75%) 37 (77%) 35 (73%) 0.63

revious cardioversions 15 (16%) 7 (14%) 8 (17%) 0.21uration of atrial flutter

(hours)�48 48 (50%) 24 (50%) 24 (50%) 1.00�48 48 (50%) 24 (50%) 24 (50%) 1.00ody mass index (kg/m2) 25 � 4.7 26 � 5.0 24 � 4.3 0.38ody surface area (m2) 2 � 0.2 2 � 0.2 1.9 � 0.2 0.38ew York Heart

Associationclassification

I 16 (17%) 8 (17%) 8 (17%) 1.00II 34 (35%) 17 (35%) 17 (35%) 1.00III 36 (38%) 19 (40%) 17 (35%) 0.83IV 10 (10%) 4 (8%) 6 (12%) 0.73Median II II IIypertension 41 (39%) 21 (44%) 20 (42%) 0.83oronary artery disease 30 (31%) 11 (23%) 19 (39%) 0.08alvular disease 16 (17%) 5 (10%) 11 (23%) 0.17trial septal defect 10 (10%) 3 (6%) 7 (14%) 0.31ardiomyopathy (dilatative,

ischemic, etc.)5 (5%) 1 (2%) 4 (8%) 0.35

eft ventricular functionNormal 68 (70%) 36 (75%) 32 (67%) 0.50Mild dysfunction 7 (7%) 3 (6%) 4 (8%) 0.69Moderate dysfunction 17 (18%) 8 (17%) 9 (19%) 0.78Severe dysfunction 4 (4%) 1 (2%) 3 (6%) 0.29Median Normal Normal Normalntiarrhythmic drugs at

cardioversionAmiodarone 12 (12%) 5 (10%) 7 (15%) 0.75Flecainide 10 (10%) 5 (10%) 5 (10%) 1.00� blockers 23 (24%) 12 (25%) 11 (23%) 0.80Sotalol 6 (6%) 1 (2%) 5 (10%) 0.20

Data are expressed as mean � SEM or as number (percentage). Thereere no significant differences in the clinical characteristics between theroups.

he alternative electrode position. g

All continuous variables are expressed as mean � SD.he primary end point was the efficacy of the differentlectrode positions. Differences were compared using Stu-ent’s t test, the Mann-Whitney U test, and the chi-squareest. Multivariate regression analysis was performed todentify predictors of the need for high energy for successfulardioversion. Statistical significance was accepted at p �0.05.PSS version 13.0 (SPSS, Inc., Chicago, Illinois) was usedor analysis. The sample size was calculated using the-sample Student’s t test (� � 0.05, 2 sided; � � 0.2 for0% statistical power) as 90 patients/group. An interim anal-sis was planned after the inclusion of 45 patients/group50%); statistical significance was accepted at p �0.05.uring interim analysis, 96 patients had already been in-

luded in the study. After interim analysis, the study wasrematurely terminated.

esults

One hundred thirty patients were screened for possiblearticipation in this study. Ninety-six patients (72 men,ean age 62 � 12 years) were eligible and gave written

nformed consent for participation in the study. Clinicalharacteristics are listed in Table 1. The 2 groups showed noignificant differences in anthropometric data and underly-ng cardiac disease (e.g., hypertension or the use of medi-ations). Table 2 lists the reasons for exclusion from thetudy. All 96 patients could be successfully cardioverted toinus rhythm. In both the A-P and A-L groups, 2 patientseeded the maximum energy of 200 J. One patient in each

96 Patientswith common-type Atrial Flutter included

48 Patientscardioverted with

A-P electrode position

48 Patientscardioverted with

A-L electrode position

Success at:50 Joule: 1875 Joule: 19100 Joule: 8150 Joule: 1200 Joule: 2

Success at:50 Joule: 3575 Joule: 9100 Joule: -150 Joule: 2200 Joule: 2

mean energy:77 ± 13 Joule

mean energy:65 ± 13 Joule

Cross-Over:A-P A-L: 1A-L A-P: 1

Figure 1. Course of trial.

able 2easons of exclusion from trial

eason Patients

istory of atrial fibrillation 7acemaker or implantable cardioverter-defibrillator 4efused consent 10ncommon atrial flutter 7istory of heart surgery 2

nability to follow step-up protocol 4otal 34

roup needed a crossover to the alternative electrode posi-

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1549Arrhythmias and Conduction Disturbances/Electrode Position for Atrial Flutter Cardioversion

ion. The 2 patients were then successfully cardioverted byhis second final shock of 200 J (Figure 1). Cardioversionas counted as successful for the group to which the

igure 2. Cumulative cardioversion efficacy of biphasic shocks showingtop) mean energy and (middle) mean number of shocks, as well asbottom) number of successfully treated patients with first shock.

igure 3. Efficacy of cumulative cardioversion (CV) in the A-L and A-Proups.

atient was switched. No major complications, adverse n

vents, or major skin irritations were reported in the A-Pr A-L group.

The efficacy of the first shock with 50 J (Figure 2) in the-L group (35 of 48 patients [73%]) was highly signifi-

antly (p � 0.001) greater than in the A-P group (18 of 4836%]), with no significant difference (p � 0.84) in trans-horacic impedance (77 � 17 � for A-L vs 76 � 15 � for-P) between groups. The cumulative cardioversion effi-

acy for the shocks of 50, 75, 100, 150, and 200 J (73%,2%, 92%, 96%, and 100% for A-L; 38%, 77%, 94%, 96%,nd 100% for A-P) showed a significant difference only forhe 2 lowest shock strengths (p � 0.001 for 50 J and p �.04 for 75 J; Figure 3). There was no significant differenceetween groups for the higher shock strengths (p � 0.62 for00 J, p � 0.81 for 150 J, and p � 0.77 for 200 J). Multivariateogistic regression showed 3 independent variables predictinguccessful cardioversion with high energy levels: body massndex �25 kg/m2 (p � 0.003), coronary artery disease (p �.049), and valvular disease (p � 0.004).

iscussion

In our study, the A-L electrode position was superior tohe A-P electrode position. Multiple previous studies haveound an advantage of the A-P electrode position11,15,16,18,19

or the electrical cardioversion of atrial fibrillation. Thesetudies examined electrode position solely for atrial fibril-ation and lacked a defined step-up protocol. The currentuidelines for the treatment of patients with atrial flutter arencluded in the guidelines for atrial fibrillation. Atrial fibril-ation requires large amounts of myocardial tissue as aubstrate, whereas atrial flutter requires only critical aspectsf the right atrial isthmus to perpetuate, which may accountor the different successful electrode positions.

The superiority of A-L electrodes might be explained bylectroanatomic properties of the human thorax. Modernmaging technologies have demonstrated that different elec-rode positions alter the spatial distribution of peak currentelivery to myocardial tissue.20 For the A-L electrode po-ition, it was shown that this electrode placement leads to aardiac current flow entering at the frontal right atrial wallnd leaving via the inferior vena cava.21 A-L electrodesight produce the peak cardiac current flow into the reentry

ircuit of typical atrial flutter in the right atrium. In 1981,ithout knowing exactly the pathologic mechanism of typ-

cal atrial flutter,4,5,22 Kerber et al16 found the A-L electrodeosition preferable to the A-P position for cardioversion oftrial flutter. Earlier studies found increasing success ratesith increasing shock strengths.11,15,16,23,24 High shock

trengths might have a high rate of complications andhould be avoided.25 Cumulative efficacy at low shocktrengths in our study was greater with the A-L electrodeosition (Figure 3).

No differences were shown for high shock strengths�100 J). This might be due to sufficiently high shock fieldradients in the anterior portion of the thorax, as described byirchhof et al.15 Four patients needed high shock strengths of100 J despite using the A-L electrode position and biphasicaveform.From previous studies, high body mass index,26,27 coro-

ary artery disease,28 and valvular disease29 are known to

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1550 The American Journal of Cardiology (www.AJConline.org)

nfluence the success of cardioversion at high energy levels.ultivariate logistic regression of our data found a bodyass index �25 kg/m2, coronary artery disease, and valvu-

ar disease to be independent predictors of the need for highnergy for successful cardioversion in our study. All 4atients who were successfully cardioverted with highhock strengths presented with �2 of these predictors. It ismportant to note that all patients could successfully beardioverted to sinus rhythm, in contrast to previous studiesith atrial flutter15,16,30,31 or atrial fibrillation,11,15,16,24,30,31

lthough this might not be generalized to younger patients,s the study population had a mean age of 62 years.

The physicians and patients could not be blinded to thelectrode positions, because only 2 electrodes could bepplied per patient at a time for technical reasons. For safetyeasons, we decided to use self-adhesive patches. Duringur trial, another study11 showed advantages for handheldaddles over self-adhesive patches. Using handheld paddlesay have led to even less mean applied energy in the A-L

nd A-P electrode positions.

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